I was working on my Lumia wheel the other day. I decided to use some crushed glass as the medium on the wheel. I figured the best glass to use was laser grade for more output. I had a decent amount of AiXiZ, and Ca$io lens so I took a hammer and smashed one. Nothing. I hit it really hard the second time. Nothing. I hit it 3 times in a row and got a tiny chip. I ended up heating them in a 500F degree over for 30 minutes then plunged them in a cup of ice water. It shattered the lens, but they were still intact. I hit them with a hammer again and only got a few large chunks. I then threw them in a vice and crushed them another 3 or 4 times to finally get small pieces. Even then 40% of the glass was still large chunks. Its incredible how durable this glass is.

You reminded me once when out of a sudden my laser's beam profile changed to a strange shape. I took out the lens (3-element) and found out that the lens broke due to the fact that on side of it was exposed to 2.5W and the other one to -10 celsious air temperature...:/